Rental bypass for aeration tank delivers reliable, guaranteed performance during upgrade

The Ginestous-Garonne treatment plant treats wastewater for 76% of the Toulouse metropolitan area, with a capacity for 950,000 inhabitants, equivalent to around 160,000 cubic meters per day. The plant is managed by SUEZ, on behalf of Eau de Toulouse Métropole, through the company  ASTEO.

In the summer of 2023, the treatment plant needed to replace the air diffuser membranes in an aeration tank as part of an upgrade. Xylem’s rental team was commissioned to deliver a tailor-made bypass solution for the tank in just six weeks without disrupting the plant’s day-to-day operations or the work of its teams.

Delivering a bypass solution that saved energy
To reduce the environmental footprint of the bypass, Xylem’s team designed a pumping system that did not require a new generator. Instead, they repurposed the electrical power of the aeration tank’s two turbo-compressors, which were shut down during the upgrade. The pumping system was connected directly to the compressors and required no additional power supply, thanks to the high efficiency of Xylem’s Flygt pumps, which resulted in significant energy savings.




Designing two bypasses for the aeration tank
When designing the bypass solution for the aeration tank, Xylem and the technical team from the wastewater treatment plant installed two bypasses, each rated at 5,000 m3/hour. The first bypass on the inlet channel to the aeration tank included five dry-installed Flygt pumps, providing a total installed power of 260 kW. The second bypass for the recirculation zone, used to convey sludge from the clarifier tanks, included another five pumps, delivering 185 kW of total installed power.

To achieve an output of 10,000 cubic meters of rerouted water per hour, the bypass system required the installation of large-diameter suction and discharge pipes. The size of the models used (DN 400 and 600 for suction and DN 800 for discharge) reduced potential head losses.

To further increase efficiency, the pumping system uses a monitoring and control system of sensors to match the pumps’ operation to actual demand, enabling one or several pumps to be activated when needed. This also enabled both bypass zones to maintain a consistent level of wastewater.




Providing 24/7 on-call service during bypass operations
The bypass solution was installed on time and put into operation at the start of August 2023.

By partnering with Xylem’s rental solutions, the Toulouse metropolitan area successfully completed the wastewater treatment plant upgrades with no service interruptions. Over the four-month period, both bypasses operated seamlessly, ensuring the community’s needs were met without any additional greenhouse gas emissions – a significant advantage over other proposed solutions.

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